GlueX Start Counter Meeting, February 3, 2022

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GlueX Start Counter Meeting
Thursday, February 3, 2022
10:00 am EST
Zoom: 160 815 7320 Passcode: 423500


  1. Announcements
  2. Review of minutes from the last meeting
  3. Long-term detector maintenance session at the Collaboration Meeting
  4. Resolution and Calibration
  5. Action Item Review


Present: Mark Ito, Simon Taylor, Bo Yu, Beni Zihlmann

There is a recording of this meeting on the ZoomGov site. The passcode is #RFt51@4

Review of minutes from the last meeting

We went over the minutes from the meeting on January 6th without significant comment.

Long-term detector maintenance session at the Collaboration Meeting

We decided (by a majority of those present) that Beni should give the talk, called for in this email from Matt Shepherd, on Start Counter maintenance at the February meeting.

Dark Rate Test

Beni showed the latest version of his analysis of dark rate in the start counter as a function of time. The figure is shown below.

SC DarkRate Test

The ratio plotted is the average of the ratios from the 30 start counters. The individual counter ratio is that of the area of a Gaussian fit to the pedestal distribution using only the low-side of the distribution to the total number of counts in the distribution. The Gaussian fit is insensitive to the high-side tail and thus underestimates the area of the pedestal distribution. The more area contained in the high-side tail, the lower the ratio.

  • There is no recovery of the dark rate between runs according to these data. Yi Qiang had seen some recovery in the SiPMs he tested.
  • We need to see if this increase in the noise affects timing resolution.

Resolution and Calibration

Bo showed several validation plots from calibrations Sean Dobbs has performed recently for the SRC run. See his slides for the plots. He showed timing offsets and resolution as a function of run number averaged over all counters as well as those for the individual counters. He also includes a list of problem runs that need further investigation.